Feb. 14, 2012 -- A new study shows that as little as a week in a place with high levels of air pollution raises the risk of
heart attack.

The additional risk is slight compared with classic heart attack risk factors like high blood pressure, smoking, or diabetes. But researchers say it's significant because many people are exposed to air pollution, and heart disease is the leading cause of death in industrialized countries.

"Thus, an improvement in air quality could have a significant effect on public health," researcher Hazrije Mustafic, MD, MPH, of the University of Paris Descartes, and colleagues write in the Journal of the American Medical Association.

Air Pollution Linked to Heart Attacks

Researchers say the potentially dangerous effects of high air pollution on health have been suspected for many years. But this is the first study to show even short-term exposure to air pollution is enough to increase the near-term risk of heart attack.

In their study, researchers analyzed the results of 34 studies on the association between short-term exposure to air pollution (up to seven days) and the subsequent risk of heart attack.

The air pollutants included in the review were ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and particulate matter.

The results showed all major air pollutants, with the exception of ozone, were associated with a slight increase in heart attack risk.

Researchers say there are several possible explanations for the association between air pollution and heart attack.

For example, previous studies have shown that exposure to air pollution increases inflammation, which is linked to heart attack risk.

In addition, research has shown that exposure to air pollution may increase the heart rate and may make the blood more likely to form potentially dangerous clots.